This invention generally relates to the administration of parenteral fluids to a patient by means of an intravenous (IV) set and particularly to an improved means for mounting a drop sensing unit to a drip chamber dedicated to the particular IV delivery instrument.
An IV set for the administration of parenteral fluids generally comprises a drip chamber, a length of clear plastic tubing attached to the discharge end of the drip chamber, one or more clamps to adjust the fluid flow through the clear plastic tubing and a means at the distal end of the tubing for mounting a hypodermic needle which will be inserted into the patient's vein or artery. The drip chamber is generally cylindrically shaped and is provided with a pointed hollow element (i.e., piercing element) at the top thereof which is adapted to pierce the rubber or elastomeric seal on an inverted bottle of parenteral fluid in order to drain the fluid therefrom into the drip chamber. The cylindrical wall of the drip chamber is formed from clear plastic material in order to detect fluid dripping into the chamber.
Fluid flow to the patient is usually determined by detecting the number of drops of fluid which fall into the drip chamber over a period of time and then multiplying the number of drops by a standard number used for the volume of each drop. When this method of flow rate detection is done manually, it is time consuming and frequently inaccurate.
Effective instrumentation for monitoring the drop rate into a drip chamber has been developed which comprises a light source which is positioned on one side of the clear plastic wall of the drip chamber and a photoelectric cell or other light sensor on the opposite side of the chamber wall with a light path therebetween so that the drops of parenteral fluid falling into the drip chamber intersect the light path and are thereby sensed.
With the need for greater accuracy in the delivery of parenteral fluids, particularly when drugs have been added to the fluid, the drop forming elements of the drip chamber are now carefully designed and manufactured so that the size and dropping characteristics of the fluid drops are relatively constant over a period of time and do not vary greatly from drip chamber to drip chamber. To insure that drip chambers of known drop characteristics are used with a particular IV delivery instrument, the means for coupling the drop rate monitor to the drip chamber have been designed so that only matched sets can be used together. Such mounting or coupling means are described in the following list of patents which is illustrative but not exhaustive.
U.S. Pat. No. 4,397,648 (Knute)
U.S. Pat. No. 4,346,606 (Channon et al.)
U.S. Pat. No. 4,321,461 (Walter et al.)
U.S. Pat. No. 4,038,982 (Burke et al.)
U.S. Pat. No. 3,500,366 (Chesney et al.)
However, by making the mounting element unique so that only matched components can be used together, the mounting has become more complicated and more difficult to operate, particularly in low light or in emergency situations when visual accuity may not be great.
Knute, in U.S. Pat. No. 4,397.648 (assigned to the present assignee) discloses an improved mounting system which insured proper positioning of the drop sensor on the drip chamber and which had self-aligning characteristics. However, even though the mounting system developed by Knute was a substantial advance, the mounting system was not convenient in many situations and correct positioning of the drop sensor was not always effected the first time mounting was attempted. Moreover, once the sensor was mounted the sensor was subject to misalignment or displacement by accidental contact with the sensor, the drip chamber or other parts of the IV set during use.
Thus there remains a need for a drop sensing unit which can easily and accurately be positioned onto a dedicated drip chamber, which has more dependable self-aligning characteristics and which is less apt to become misaligned during use due to accidental contact with the sensor, the drip chamber or other components of the IV set. The present invention satisfies this need.